--- a/taskcluster/taskgraph/transforms/l10n.py
+++ b/taskcluster/taskgraph/transforms/l10n.py
@@ -127,30 +127,29 @@ l10n_description_schema = Schema({
     # passed through directly to the job description
     Optional('attributes'): job_description_schema['attributes'],
     Optional('extra'): job_description_schema['extra'],
 })
 
 transforms = TransformSequence()
 
 
-def _parse_locales_file(locales_file, platform=None):
+def _parse_locales_file(locales_file, platform):
     """ Parse the passed locales file for a list of locales.
-        If platform is unset matches all platforms.
     """
     locales = []
 
     with open(locales_file, mode='r') as f:
         if locales_file.endswith('json'):
             all_locales = json.load(f)
             # XXX Only single locales are fetched
             locales = {
                 locale: data['revision']
                 for locale, data in all_locales.items()
-                if 'android' in data['platforms']
+                if platform in data['platforms']
             }
         else:
             all_locales = f.read().split()
             # 'default' is the hg revision at the top of hg repo, in this context
             locales = {locale: 'default' for locale in all_locales}
     return locales
 
 
@@ -259,17 +258,19 @@ def handle_keyed_by(config, jobs):
         for field in fields:
             resolve_keyed_by(item=job, field=field, item_name=job['name'])
         yield job
 
 
 @transforms.add
 def all_locales_attribute(config, jobs):
     for job in jobs:
-        locales_with_changesets = _parse_locales_file(job["locales-file"])
+        locales_platform = job['attributes']['build_platform'].rstrip("-nightly")
+        locales_with_changesets = _parse_locales_file(job["locales-file"],
+                                                      platform=locales_platform)
         locales_with_changesets = _remove_locales(locales_with_changesets,
                                                   to_remove=job['ignore-locales'])
 
         locales = sorted(locales_with_changesets.keys())
         attributes = job.setdefault('attributes', {})
         attributes["all_locales"] = locales
         attributes["all_locales_with_changesets"] = locales_with_changesets
         yield job